The P-50 Specialized Population Research Center described in this proposal is made up of co-investigators from the staff of one of the functional units of the Population Council--the Center for Biomedical Research. The research conducted by the scientists in this center covers the following broad areas of overlapping interest: The mechanism of androgen action will be investigated in mouse kidney and in Sertoli cells grown in culture. Hormones that act synergistically with testosterone on these tissues will be investigated. The possibility that multiple hormones influence androgen action via the androgen receptor will be investigated. A series of studies on sperm maturation and fertilization will be conducted so as to delineate a variety of biochemical markers for spermatogenesis. In addition, the sperm binding site on zona pellucida will be delineated and its cellular origin determined. Finally, the hormonal control of pregnancy will be investigated so as to delineate the interrelationship of the ovary and the fetoplacental unit.